From: Fan Du Date: Tue, 26 Mar 2013 23:24:51 +0000 (+1100) Subject: include/linux/fs.h: disable preempt when acquire i_size_seqcount write lock X-Git-Tag: next-20130402~2^2~349 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=11b5ffcd853892599ad70998f259aafc45e415ae;p=karo-tx-linux.git include/linux/fs.h: disable preempt when acquire i_size_seqcount write lock Two rt tasks bind to one CPU core. The higher priority rt task A preempts a lower priority rt task B which has already taken the write seq lock, and then the higher priority rt task A try to acquire read seq lock, it's doomed to lockup. rt task A with lower priority: call write i_size_write rt task B with higher priority: call sync, and preempt task A write_seqcount_begin(&inode->i_size_seqcount); i_size_read inode->i_size = i_size; read_seqcount_begin <-- lockup here... So disable preempt when acquiring every i_size_seqcount *write* lock will cure the problem. Signed-off-by: Fan Du Signed-off-by: Andrew Morton --- diff --git a/include/linux/fs.h b/include/linux/fs.h index 0dc32bbb8b6c..4c4f0e488313 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -675,9 +675,11 @@ static inline loff_t i_size_read(const struct inode *inode) static inline void i_size_write(struct inode *inode, loff_t i_size) { #if BITS_PER_LONG==32 && defined(CONFIG_SMP) + preempt_disable(); write_seqcount_begin(&inode->i_size_seqcount); inode->i_size = i_size; write_seqcount_end(&inode->i_size_seqcount); + preempt_enable(); #elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT) preempt_disable(); inode->i_size = i_size;